Yes, if you wish to create binary PCKS7, then you would use Chilkat Crypt. The code is the same as for encrypting with one certificate, except that the AddEncryptCert method should be called once per certificate prior to encrypting. (see http://www.chilkatsoft.com/refdoc/csCrypt2Ref.html )

If producing S/MIME is desired, then it can be accomplished using Chilkat MIME. Again, the code would be the same as for encrypting MIME with a single certificate, except that the Mime.AddEncryptCert method is called once per certificate. (see http://www.chilkatsoft.com/refdoc/csMimeRef.html )